This invention relates to irrigation/aspiration equipment.
This invention is more particulary concerned with irrigation/aspiration equipment used in a hand-held manner in a surgical setting for delivering fluid to an internal body site and removing the fluid and other debris from the same site.
Suction-irrigation cannulas are common in various configurations. They are used during surgical procedures on relatively inaccessible areas of the body, such as the interior of the eye, or in connection with laparascopic surgery and diagnostic procedures. Some of these devices have complex valve arrangements for regulating the flow from existing sources, i.e., irrigation pumps and suction units.
Current irrigation/aspiration cannulas available are known to have valving problems. These cannulas have a tendency to leak across their valves from the constant pressure differential supplied by the irrigation/suction sources. The valves also occasionally stick in one position. These deficiencies are due to the valve designs, which rely on a precise mechanical interference, e.g., sliding trumpet valves or rotary ball-style valves, that are adversely affected by the static pressure of the sources. These valve designs also create complex fluid flow paths, compromising the transfer of fluids to and from the surgical area.
A typical example is shown in U.S. Pat. No. 4,526,573, which discloses a device for controlling the delivery of irrigation or suction to a surgical site. This device includes a trumpet valve to selectively connect either the suction or irrigation line to an outlet port. Closing either line is accomplished by operating the trumpet valve so as to position one of two resilient elastomeric flanges at either end of a waisted valve member to a position between the supply line port desired to be closed and the outlet port. In this configuration, static pressure in both the suction and irrigation supply lines tends to promote leakage across the elastomeric flange, and one could expect the problem to get worse over time as the flanges wear out.
U.S. Pat. No. 4,668,215 discloses another valving system for an automatic irrigation and evacuation device for use in laparascopic procedures and general surgery. In this device, which makes use of ball-type valves, it is again seen that O-rings are used to provide sealing between the irrigation and suction supplies. A relief port is provided to minimize (but not eliminate) the pressure differential across the O-rings during operation, but again, it can be expected that operation of the valve mechanism degrades over time as the 0-rings wear out.